The invention relates to a vacuum valve comprising a valve housing with a valve opening which has an axis and is surrounded by a valve seat, a valve plate which, in an open state of valve opening, releases the valve opening and, in a closed state of the valve opening, bears against the valve seat, and a carrier unit which carries the valve plate and which is adjustable between a first position in which the open state of the valve opening is present and a second position, wherein the valve plate is connected via at least two spaced apart drive elements of the carrier unit to the carrier unit and is adjustable by the drive elements between a retracted position and an advanced position, wherein, in the second position of the carrier unit and the advanced position of the valve plate, the closed state of the valve opening is present.
Such a vacuum valve is apparent from US 2014/0021395 A1. The vacuum valve comprises first and second valve plates which close first and second valve openings in the closed state of the vacuum valve. A carrier unit which carries the valve plates is fitted on a valve rod, by the displacement of which in the direction of its longitudinal axis the carrier unit is adjusted between a first position in which the vacuum valve is open and a second position. The carrier unit has drive elements in the form of piston/cylinder units which are connected to the valve plates and adjust these in the second position of the carrier unit between a retracted position and an advanced position. In the advanced positions of the valve plates, the valve openings are closed by the valve plates. The valve plates are formed so as to be removable from the carrier unit without tools, wherein mushroom-shaped heads of the valve rods can be inserted into receiving slots of receiving parts for connection of the valve plates to the carrier units and at least one of the receiving parts is rotatable in order to fix the valve plate in the pushed-on state.
Further vacuum valves with first and second valve plates borne by a carrier unit, wherein the carrier unit has drive elements for adjustment of the valve plates, are apparent from WO 2011/096613 A1, KR 10-2010-0061214 and US 2006/0225811 A1. A vacuum valve with a single valve plate which is borne by drive elements of a carrier unit is apparent from U.S. Pat. No. 6,899,316 B2. US 2004/0079915 A1 and U.S. Pat. No. 6,561,484 B2 show vacuum valves in which a valve plate and an opposite supporting plate are borne by a carrier unit and are adjustable by drive elements. In the closed state, the supporting plate is supported on the valve housing in order to press the valve plate onto the valve seat.
In the case of valve plates connected to drive elements of a carrier unit, a certain degree of play or a certain degree of mobility of the valve plate is normally permitted. As a result, tolerances can be accepted in order, in the closed state, to achieve uniform pressing of the elastic seal arranged on the valve plate onto the sealing face of the valve seat. Different degrees of expansion of the valve plate and the carrier unit in the case of temperature changes, for example, when heating up the vacuum valve, can also be accepted as a result.
In the case of a removable formation of the valve plates, as is apparent, for example, from US 2014/0021395 A1, degrees of mobility between the valve plate and the carrier unit also occur as a result of play in the connecting devices.
Precisely in the event of the presence of a degree of mobility or play between the carrier unit and the (respective) valve plate and/or in the case of large, heavy valve plates, as are used in vacuum valves with large opening widths, movements occur between the valve plate and the carrier unit during adjustment of the carrier unit between the first and second position as a result of the occurring accelerations. Undesirable particle productions occur in the vacuum as a result of the parts which rub on one another in this case and this can also result in undesirable development of noise. However, even in the case of a screwing of the valve plate with parts of the carrier unit bearing the valve plate, for example, piston rods of drive elements, vibrations of the valve plate occur during adjustment of the carrier unit between the first and second position as a result of the active accelerations, which involves micro-movements between the parts, which are connected to one another, of the valve plate and the carrier unit so that undesirable particles are generated in the vacuum.